Antibodies immunoreactive with heregulin-coupled her3

ABSTRACT

Antibodies which specifically bind heregulin-coupled HER3, at a site distinct from the heregulin binding site, are described. These antibodies are particularly useful in treating cancer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. provisional application61/173,670 filed 29 Apr. 2009. The contents of this document areincorporated herein by reference.

TECHNICAL FIELD

The invention relates to monoclonal antibodies with superior therapeuticvalue. The antibodies of the invention are particularly selective forcancer cells, and more particularly for cancer cells that secretecertain autocrine growth factors.

BACKGROUND ART

A family of receptors that mediate signaling through tyrosine kinasesincludes a subfamily of at least four members: HER1 also designatedepidermal growth factor receptor (EGFR) is encoded by the ErbB1 gene;HER2 or HER2/neu encoded by the ErbB2 gene, HER3, encoded by the ErbB3gene and HER4, encoded by ErbB4. Each of these receptors has amultiplicity of synonyms and in the present application, the “HER”terminology and ErbB terminology will be used interchangeably for allthe factors, whether discussing protein or nucleic acids.

The primary natural ligand for the receptor encoded by ErbB3 isheregulin (HRG), a polypeptide that, when bound to HER3 induces aconformational change that promotes dimerization of HER3 with HER2through the extracellular domains of each activating the signalingcascade, as shown in FIG. 1A. A similar dimerization is stimulated bythe ligand for the HER1 receptor, Epidermal Growth Factor (EGF), whichalso activates a signaling cascade intracellularly.

Antibodies, including monoclonal antibodies to HER3 have been prepared.U.S. Pat. No. 5,480,968 discloses antibodies that bind specifically toErbB3 and do not bind to ErbB2 or ErbB1. U.S. Pat. No. 5,968,511discloses and claims antibodies that bind to HER3 and reduceheregulin-induced formation of an HER2-HER3 protein complex in cellsthat express both of these receptors or which antibodies increase thebinding affinity of heregulin for ErbB3 protein or which reduceactivation of the downstream signaling. Although only murine antibodiesare prepared, humanized antibodies are also claimed.

Published U.S. application 2004/0197332 describes and claims anti-HER3antibodies that downregulate the expression of HER3. PCT PublicationWO2007/077028 describes antibodies that bind to HER3 that are producedin XenoMouse® and are thus fully human by sequence. Most of theseantibodies are described as binding to the major ligand binding domain(L2) of the extracellular domain of HER3, but the binding is destroyedif the three-dimensional structure of the extracellular domain isdisrupted. Further, the antibodies described in this publication competewith HRG for binding to HER3.

DISCLOSURE OF THE INVENTION

It has now been found possible to obtain antibodies that bind at a muchhigher affinity to HER3 when it is complexed with heregulin than touncomplexed HER3. Such antibodies are particularly valuable since theyare most effective in the context of tumor cells that secrete heregulinor analogous agonist peptides, thus stimulating the signaling cascade ata higher level than in normal cells. This enhances the specificity ofthe treatment to those tumor cells that are most aggressive in theirinvasive growth properties, while minimizing toxicity to normal cellsthat are not being intensively stimulated. Further, the novel antibodiesare effective at blocking signaling in cells that over-express HER1 andHER3, providing a desirable “pan-HER” activity (Huang, Z, et al., ExpertOpin Biol Ther. (2009) 9:97-110).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams of the interaction of HER2 and HER3 in thepresence of heregulin (FIG. 1A) and in the presence of both heregulinand either antibody 14B10 or antibody 1G4 (FIG. 1B).

FIGS. 2A and 2B are graphs showing a comparison of binding of 1G4 mAband 14B10 mAb to the heregulin active complex with HER3 as measured byFortéBio® biosensor.

FIGS. 3A and 3B show the ability of various antibodies directed againstHER3 to inhibit the growth of MCF-7 carcinoma cells and to inhibittyrosine phosphorylation in these cells.

FIG. 4 shows the ability of various anti-HER3 antibodies to inhibitMCF-7 cell proliferation.

FIG. 5 shows that activity by the tyrosine phosphorylation measure ofactivity is not predictive of anti-proliferative activity.

FIG. 6 shows the ability of various antibodies directed against HER3 toinhibit tyrosine proliferation in MB 468, a cell line thatover-expresses HER1 and HER3 rather than HER2 and HER3.

FIG. 7 shows the nucleotide sequence encoding 1G4 heavy chain (SEQ IDNO:______) and 1G4 light chain (SEQ ID NO:______) and deduced amino acidsequences (SEQ ID NO:______ and SEQ ID NO:______).

MODES OF CARRYING OUT THE INVENTION

The present invention provides monoclonal antibodies with uniquespecificities for the heregulin-bound active form of HER3, thus,preferentially inhibiting dimerization and downstream signaling inenvironments with high concentrations of heregulin. Such highconcentrations characterize many tumor cells. By targeting cells bathedin a high local concentration of stimulatory ligand, toxicities arisingfrom blocking signaling from lower concentrations in normal cells can beminimized (Bria, E, et al., Expert Opin Biol Ther. (2008) 8:1963-1971).

The use of antibodies that preferentially bind a HER3:heregulin complexis advantageous since they are most effective on cells, such as cancercells that are dependent on the complex signaling for growth. This typeof cell is characteristic of many tumors.

Thus, the invention is directed to monoclonal antibodies andpharmaceutical compositions thereof wherein these antibodies bind toheregulin activated HER3 with an affinity at least five times theiraffinity for HER3 not bound to heregulin, preferably ten times greater,at all values between 5 and 10, and at values greater than 10.Preferably, the affinity of the antibody will be at least thatrepresented by a kD of 5 nM for HER3 itself, more preferably thatrepresented by a kD of at least 2 nM and more preferably thatrepresented by a kD of 100 pmol.

The monoclonal antibodies may take many forms, including chimeric formswherein the variable regions are of one species and the constant regionsof another; forms consisting only of the variable regions, single-chainforms; and the like. Thus, “antibodies” refers both to whole antibodiesand to fragments thereof that exhibit the required immunospecificity. Insome cases, this is spelled out, but if not, fragments are intended tobe included in this term unless it is otherwise obvious from context.

The antibodies of the invention can be obtained by extensive screeningof hybridomas or immortalized cells of laboratory animals such as rats,mice and rabbits immunized with appropriate immunogens. Appropriateimmunogens include those exemplified below, as well as portions of theHER3 protein that have been treated with heregulin. The antibodies thusproduced are screened for their ability to bind heregulin-bound HER3differentially from HER3 itself. These antibodies can then be humanizedusing procedures now commercially available to obtain antibodiessuitable for administration to humans.

In one particular example set forth below, an antibody with thisdesirable differential binding affinity, 1G4, was prepared. Humanizedforms and human analogs of this antibody are included within the scopeof this invention.

The hybridoma that produces IG4 was deposited with the American TypeCulture Collection, 10801 University Boulevard, Manassas, Va. 20110,under the terms of the Budapest Treaty on 29 Apr. 2010. Upon issuance ofa U.S. patent disclosing this hybridoma, all restrictions on thisdeposit will be irrevocably removed.

In addition, FIG. 7 shows the nucleotide sequence and amino acidsequences of the heavy chain and light chain of 1G4 respectively. TheCDR of the heavy chain are: CDRH1:GYTFTDYVS (SEQ ID NO: ______);CDRH2:IYPSGRY (SEQ ID NO: ______); CDRH3:TRSLQRLRYFDV (SEQ ID NO:______). The CDR of the light chain are CDRL1:RASQSISDYLH (SEQ ID NO:______); CDRL2:YGSQSIS (SEQ ID NO: ______); CDRL3:QQSNSWPLT (SEQ ID NO:______).

Alternatively, laboratory animals that produce human antibodies directlycan be used as subjects to produce antibodies that are human. Thus, theimmunogen can be administered to animals such as the XenoMouse® thatwill provide directly the human antibodies desired. These antibodies arescreened in a manner similar to that employed in screening hybridomas orother immortalized rodent cells.

Typical procedures simply compare the measured affinity of the variousantibodies in the screen with respect to HER3 and HER3 coupled toheregulin. A variety of assays is appropriate for this, andstraightforward commercially available assays include those marketed asBiacore™ and FortéBio®.

Preferably, however, the proprietary technology CellSpot™ described inU.S. Pat. No. 7,413,868 incorporated herein by reference may be used.This permits millions of hybridomas and splenocytes or lymphocytes to bescreened in practical time frames.

Suitable antibodies can also be obtained directly from human beings,since individuals harboring tumors, for example, that produceheregulin:HER3 complexes will generate antibodies to these tumorantigens. In general, antibodies immunospecific for tumor antigens areproduced by such subjects. See, for example, Pavoni, E., et al., BMCBiotechnology (2007) 770:1-17. In addition, patients with autoimmunediseases such as lupus make antibodies to cell antigens not necessarilyassociated with tumors. Because of the large number of cells that can besampled, even very rare antibodies can be obtained in this fashion.

When suitable cells secreting the desired antibodies have beenidentified in the screen, the antibodies can then be producedrecombinantly using well known techniques. The nucleotide sequencesencoding the antibodies are obtained from cells secreting them andsuitable expression constructs prepared to transfect host cells for suchrecombinant production. The ability to produce such antibodiesrecombinantly permits variants such as single chain antibodies to beproduced. A variety of cells can be used for such production includinginsect, mammalian and plant cells, as well as microorganism cultures.

The antibodies of the invention, and fragments thereof, in particular,human and humanized forms of them, are useful in treating cancers thatare associated with heregulin-stimulated signaling. These includecancers of the breast, uterus, ovary, prostate, kidney, lung, pancreas,stomach, salivary gland, colon, colon-rectal, thyroid, bladder, skin, orany cancer exhibiting heregulin-stimulated proliferation. It may beuseful to evaluate the cancer to be treated for its ability to secreteheregulin in connection with conducting treatment using the antibodiesof the invention. This may be done by culturing cells from a biopsiedcancer sample or by in situ testing of the tumor in vivo. In one method,this is done by contacting said tumor or biopsy thereof with theantibodies or fragments of the invention and determining the level ofcomplex formed as compared to any complex formed with antibodies thatbind to uncoupled HER3.

The subjects may be human or veterinary, including, domestic animalssuch as dogs and cats, farm animals such as pigs, cows and sheep; andlaboratory model animals such as rats, mice and rabbits. Laboratorymodel animals may be particularly useful in evaluating the effect of theantibodies of the invention in the corresponding human tumors, and suchuse is included within the invention.

For use in treatment, the antibodies of the invention may also becoupled to cytotoxic agents and/or to anti-tumor drugs in general. Suchdrugs include, for example, platinum-based drugs, cell cycle inhibitors,natural products such as vincristine and various camptothecins.

For administration, the antibodies are formulated according to standardprocedures for pharmaceutical compositions of antibodies such as thosedescribed in Remington's Pharmaceutical Sciences, Mack PublishingCompany, Easton Pa., latest edition. These formulations may includedelivery vehicles such as liposomes or micelles or may contain standardexcipients, such as saline or saccharides.

Typically, the antibody compositions are administered by injection, inparticular intravenous injection. However, any mode of administrationthat is workable with such compositions is included within the scope ofthe invention.

The production of the antibodies on a practical scale may includestandard recombinant methods wherein the nucleotide sequences encodingthe antibodies or portions thereof have been isolated and manipulated instandard procedures to obtain the active antibody compositions. Suchproduction is typically in mammalian cell culture, insect cell cultureor plant cell culture or may be by plants per se. The antibodies of theclaimed characteristics are included within the scope of the inventionsregardless of means of production.

The following examples are intended to illustrate but not to limit theinvention.

EXAMPLE 1 Production of 1G4 and Binding Assay

Seven murine hybridoma libraries were prepared by immunizing mice with293 cells overexpressing HER3 extracellular domain (ECD) along with apolypeptide which consists essentially of the L2 domain of HER3 that hadbeen produced in E. coli, and fusion of the immunized B cells with amurine myeloma by standard methods. About 400 million hybridoma cellswere screened for immunoactivity with HER3 in the presence and absenceof heregulin, of which about 700 were positive for binding to both byinitial ELISA assay and about 70 by FACS analysis for binding to intactcells. The screening employs the assays in the above cited U.S. Pat. No.7,413,868.

Of these, six of these murine antibodies were assayed quantitatively fortheir binding affinities to HER3 ECD according to the commerciallyavailable FortéBio® method. In this method, ECD at 10-15 μg/ml wascaptured onto an amine-reactive surface in 10 mM MES, pH 6.0 at 25° C.Binding capacity is tested by treating the surface with unlabeledantibody. As unlabeled antibody accumulates on the surface, the opticalcharacteristics of the surface are changed, thus allowing measurement ofmass accumulation without requiring labeling. This is a modification ofthe Biacore™ style analysis. The antibodies were tested at 67 nM as thehighest concentration and diluted in a three-fold dilution series.Response data for the various concentrations were individually andglobally fitted to determine the binding affinities. The results forbinding to HER3 ECD are summarized in Table 1

TABLE 1 Binding to HER3 ECD kD (pM) Average Stdev 14B10 18 4 1G4 2,8102,660 P1G1 115 89 C27.1 281 168 C31.1 349 185 A28 2,140 2,500 heregulin165,000 111,000

As shown, 14B10 showed the highest affinity but all of the sixantibodies bound in the pM or nM range.

The binding assay was repeated for two of the antibodies, 1G4 and 14B10using the same FortéBio® method. HER3 ECD at 10-15 μg/ml was againcaptured onto the amine surface in the same buffer. Heregulin at 10μg/ml was added to form the HER3:heregulin complex on the surface andthe antibodies tested at 67 nM once again using three-fold dilutionseries and the data were fitted to determine binding constants. Theseare listed in Table 2

TABLE 2 Binding to HER3-Heregulin Complex kD (pM) Average Stdev 1G4 327113 14B10 34 15

Antibody 14B10 bound to HER3:heregulin complex at about the sameaffinity as to HER3. Antibody 1G4 bound to HER3 alone with an affinityof 2.8 nM, but to the HER3:heregulin complex with an affinity of 327 pM.In both cases, the binding affinity for HER3 was tighter than that ofheregulin itself which binds to HER3 ECD with an affinity of 165 nM.

A diagram contrasting the apparent mode of action of these antibodies isshown in FIG. 1B.

FIGS. 2A and 2B show a comparison between 1G4 and 14B10 in their abilityto bind the complex of HER3 ECD with heregulin. As shown in FIG. 2A, 1G4is able to bind the complex differentially, whereas 14B10 (FIG. 2B) doesnot.

EXAMPLE 2 Effect on Tumor Cells

In addition, the ability of various antibodies to inhibitphosphorylation of tyrosine in HER3 and to inhibit cell growth in MCF-7breast carcinoma cells cultured with heregulin was tested at variousantibody concentrations.

To assess the ability of the antibodies to inhibit downstreamphosphorylation, MCF-7 cells were maintained in log phase and fortesting the medium was aspirated and the cells were rinsed, 2-3 ml oftrypsin was added and the mixture incubated at 37° C. for 5 minutes.Trypsinization was stopped by adding 10-12 ml of growth medium and thecells were suspended for counting using a Becton Dickenson Vi-CELL™ cellcounter and then plated at 10⁴ cells/well in 96-well plates at 100μl/well. The plates were centrifuged at 960 rpm for 5 minutes andincubated at 37° C. for 4 hours, after which the medium was replacedwith serum-free medium at 100 μl/well and the cells returned to theincubator for 3 days.

For the assay, purified antibodies at 1 μg/ml were added to each welland incubated at 37° C. for 1 hour, after which 20 nM heregulin 1b wasadded for 10 minutes to some of the wells. The media were aspirated fromthe cell surface and lysis buffer was added for determination of HER3phosphorylation.

For this determination, a 96-well Greiner plate was coated with 2 μg/mlcapture antibody in PBS at 100 μl/well and incubated at 4° C. overnight.The plate was then washed with PBST, blocked with 200 μl/well 3% BSA andPBS, washed twice with 300 μl PBST. Eighty μl of the cell lysateprepared in the previous paragraph was added to each well and incubatedat room temperature with a rotator for 2 hours. The plate was thenwashed with PBST and then incubated with anti-phosphotyrosine labeledwith horseradish peroxidase at 1:2000 for 2 hours. After washing,LumiGlo™ peroxidase solution KPL catalog number 54-61-00 was added at100 μl/well and the extent of phosphorylation determinedspectraphotometrically. The results are shown in FIG. 3A. As shown inthese results, the IC₅₀ for 1G4 is about 10 ng/ml; whereas that for twoother antibodies, E7 and C31, was much higher.

To assess effects on cell proliferation, MCF-7 cells were grown inflasks until confluent, then trypsinized and collected in growing mediato stop trypsinization. The cells were then washed with starving media3-4 times.

Sterile 96-well black clear-bottom plates were provided with 50 μl ofstarving media per well and incubated for 15 minutes at 37° C. Theantibodies to be tested were diluted as desired in starving medium andseeded at 5,000 cells/50 μl into individual wells. The cells wereincubated with antibody for 30 minutes at 37° C. and then 3 nM HRGadded. The cells were then cultured for 5-6 days and cell proliferationmeasured by adding fluorescent dye Resazurin™ at 1:10 and incubated for3 hours at 37° C. The plates were read on a fluorescent plate reader at531/590 nm. The results are shown in FIG. 3B.

As shown, 1G4 had an EC₅₀ between 0.1 μg/ml and 1 μg/ml; only 14B10 hada lower EC₅₀.

As shown in FIG. 4, several of the antibodies including 1G4 were alsoable to block migration of cells stimulated with heregulin.

It is important to note that inhibition of tyrosine phosphorylation doesnot guarantee or evaluate inhibition of proliferation, as shown in FIG.5. Prior art teachings cited above have assumed that the two activitieswould be tightly correlated. By surveying 400 million hybridoma cellsfrom seven libraries, a more comprehensive view of the activities wasobtained, and lack of correlation established.

EXAMPLE 3 Effect on Tumor Cells Expressing HER1

The novel antibodies also inhibit tyrosine proliferation in a cell linethat over-expresses HER1 and HER3, with no detectable HER2: MB468, humanbreast adenocarcinoma (Moasser, M. M., et al., Cancer Res (2001)61:7184-7188). The cells were plated at 5,000 cells in 100 μl inDMEM/F12 50/50 plus 0.02% BSA-Transferrin. Under these conditions,titration of heregulin stimulation of proliferation established that 3nM achieves 80% of the maximal stimulation. Antibody inhibition wasthereby measurable along the linear dose/response part of thestimulation curve. The cells were cultured for 5 days and cellproliferation measured by adding fluorescent dye Resazurin™ as in theprevious Example. The results are shown in FIG. 6. As shown, IG4, 14B10and A28 have similar EC₅₀'s at approximately 10⁻³-10⁻² μg/ml. P1G1,however, has an EC₅₀ of about 10⁻¹ μg/ml. Activity of the antibodies wasthen verified at 30 nM heregulin stimulation.

1. Monoclonal antibodies including fragments and recombinant formsthereof which bind to HER3:heregulin complex with greater affinity ascompared to uncomplexed HER3.
 2. The antibodies or fragments of claim 1which bind to HER3 with an affinity of at least 5 nM and bind to aHER3:heregulin complex with an affinity at least 5 times that of bindingto HER3.
 3. An antibody of claim 1 which is 1G4 or a fragment thereof.4. The antibodies of claim 1 which are human or humanized.
 5. Theantibodies of claim 1 which are prepared recombinantly.
 6. Theantibodies of claim 5 which are single chain antibodies.
 7. Conjugatesof the antibodies or fragments of claim 5 coupled to a cytotoxic agent.8. Conjugates of the antibodies of claim 5 coupled to a chemotherapeuticagent.
 9. A pharmaceutical composition that contains the antibodies orfragments of claim
 5. 10. A pharmaceutical composition that contains theconjugates of claim
 7. 11. A method to treat cancer in a subject whichmethod comprises administering to a subject in need of such treatment aneffective amount of the antibodies of claim
 5. 12. A method to treatcancer in a subject which method comprises administering to a subject inneed of such treatment an effective amount of the conjugates of claim 7.13. The method of claim 11 wherein the subject is human and saidantibodies are human or humanized.
 14. The method of claim 12 whereinthe subject is human and said antibodies are human or humanized.
 15. Themethod of claim 11 which further includes assessing the tumor of saidsubjects for the presence of a HER3:heregulin complex.
 16. The method ofclaim 12 which further includes assessing the tumor of said subjects forthe presence of a HER3:heregulin complex.
 17. A method to assess a tumorfor the presence of a HER3:heregulin complex which comprises contractingsaid tumor or biopsy thereof with the antibodies or fragments of claim 1and determining the level of complex formed as compared to any complexformed with antibodies that bind to uncoupled HER3.
 18. The antibodiesor fragments of claim 1 having heavy chain CDR1:GYTFTDYVS (SEQ ID NO:4),CDR2:IYPSGRY (SEQ ID NO:5) and/or CDR3:TRSLQRLRYFDV (SEQ ID NO:6). 19.The antibodies or fragments of claim 1 having light chainCDR1:RASQSISDYLH (SEQ ID NO:10), CDR2:YGSQSIS (SEQ ID NO:11) and/orCDR3:QQSNSWPLT (SEQ ID NO:12).